In an active organic light emitting diode display system, the glow brightness of an organic light emitting diode (OLED) is proportional to a driving current, and has an exponential relationship with a driving voltage signal. Therefore, under a low grayscale display state, the variation of its glow brightness is very sensitive to the variation of the driving voltage signal. In an AMOLED (Active Matrix/Organic Light Emitting Diode) display panel, signal transmission loss on a power signal line will cause a variation of the driving voltage signal of the OLED device, thus effecting display uniformity. Therefore, a compensation technique is often introduced into the design of the backplate circuit to compensate it, wherein an external compensation is a mode that is often adopted. The external compensation is implemented by adopting a pixel circuit having a compensation function cooperating with a customized driving chip. The adopted pixel circuit structure is for example 3T1C or 4T2C, etc. The initiation of the compensation mechanism often needs a peripheral module circuit to provide a special module to complete.
As for the compensation of IR drop on the power line, it needs to conduct sampling first. A sampled signal may be a current signal or a voltage signal. The sampled signal needs to be judged necessarily to confirm whether a compensation operation needs to be conducted. For example, if ΔV caused by IR drop is greater than a gray scale driving voltage difference, then compensation is needed. After judging the sampled signal, if compensation is needed, then a compensation voltage generator is started to generate a compensation voltage signal, which is fed back to the pixel circuit having a compensation function design on a timing signal control line of the driving chip to implement the compensation of IR drop on the power line.